1. Field of the Disclosure
The present disclosure relates generally to the bonding of wire to semiconductor devices and, more particularly, to wire bonding using a capillary.
2. Description of the Related Art
Wire bonding is used to form wire connections between pads of a semiconductor device and pads of a substrate (e.g., an interposer or printed circuit board), between a semiconductor device and a lead frame or between two semiconductor devices. A wire bonding tool uses an external electrode to form a metal ball, via electric flame off (EFO) at the end of a feed wire. This metal ball is then placed in contact with a bond pad via a capillary and bonded with the bond pad through a combination of heat, pressure, and ultrasonic vibration energy. In certain implementations, such as the bonding of copper wire to aluminum pads, this process can result in metal material of the bond pad being pushed out and away from the ball bond site. This displaced metal, or “splash,” can result in a short-circuit to adjacent bond pads. Moreover, this splash can prevent adequate welding between the ball and the bond pad substrate, which can lead to a crevice forming at the edge of the ball-pad bond (hereinafter, “ball bond”). This crevice can result in accelerated corrosion of the intermetallic coverage (IMC) formed between the ball and pad. Moreover, this crevice also can fill with mold compound resin during the device packaging process. The thermal expansion of the mold compound in the crevice can weaken, and subsequently lead to the failure of, the ball bond. In either event, the reliability of the resulting semiconductor device can be compromised by the pad metal splash generated by conventional wire bond techniques.